Organic light emitting diode, OLED display device with self-luminous, low driving voltage, high luminous efficiency, short response time, sharpness and high contrast, nearly 180° viewing angle, wide temperature range for using, realizing flexible display and large area full color display and many other advantages, is recognized as the most potential for development in the display device industry.
The OLED display devices can be divided into two types, including passive matrix OLED (PMOLED) and active matrix OLED (AMOLED) according to the driving mode, such as two types of direct addressing and Thin Film Transistor, TFT matrix addressing. Among them, AMOLED has pixels arranged in an array type that is active display type with high luminous efficiency, and usually used for high-definition large-size display device.
AMOLED is the current driving device, when a current flows through the organic light-emitting diode, the organic light-emitting diode emitting light, and the luminous brightness is decided by current flow through the organic light-emitting diode itself.
Most of the existing integrated circuit, IC transmits only voltage signals, so the driving circuit for the pixels of the AMOLED needs to complete the task of converting the voltage signal into a current signal.
Referring to FIG. 1, FIG. 1 is a circuit diagram of the pixel driving circuit of the AMOLED in the conventional technology includes: a first thin film transistor T10, a second thin film transistor T20, a third thin film transistor T30, a fourth thin film transistor T40, a capacitor C10, and an organic light emitting diode D10, a gate of the first thin film transistor T10 receives a first scanning signal Scan1, a source receives a data signal Data, a drain is electrically connected to a gate of the second thin film transistor T20, a drain of the second thin film transistor T20 receives power supply voltage OVDD, a source is electrically connected to an anode of the organic light emitting diode D10, a gate of the third thin film transistor T30 receives a second scanning signal Scan2, a source is electrically connected to the gate of the second thin film transistor T20, a drain is electrically connected to a source of the thin film transistor T40, a gate of the fourth thin film transistor T40 receives the second scanning signal Scan2, a source receives an initialization voltage Vini, a drain is electrically connected to the anode of the organic light emitting diode D10, an end of the capacitor C10 is electrically connected to the gate of the second thin film transistor T20 and the other end is electrically connected to the anode of the organic light emitting diode D10, and the cathode of the organic light emitting diode D10 is grounded. The pixel driving circuit of the AMOLED performs the four stages successively of reset, threshold voltage detection, threshold voltage compensation, and emitting light to complete the driving of pixels, to realize the compensation for the characteristic of the drift of the threshold voltage of the driving thin film transistor, i.e., the second thin film transistor T20, however, due to the initialization voltage Vini in the AMOLED pixel driving circuit is always low electrical level, so that the source voltage of the fourth thin film transistor T40 at the light emission stage is lower than the voltage of the gate and the source of the second thin film transistor T20, and then leading to the gate and the source of the second thin film transistor T20 generate a leakage current, and the presence of the leakage current causes the OLED compensation data to be drifted and the gate and source voltage of the second thin film transistor T20 are distorted to affect the compensation effect.